1. Field of the Invention
This invention relates to a water purification device in which raw water may be purified by filtration from the periphery of the filter medium layer and more particularly to such device in which a continuous raw water channel may be provided by a raw water channel forming plate extending spirally on the inner wall of the filter tank.
2. Description of the Prior Art
A water purification device in which a plurality of raw water channel forming plates are mounted in tiers along the inner wall of the filter tank, and in which a collector for collecting filtered water is mounted substantially at the center of the filter medium layer for purifying raw water by filtration from the periphery of the filter medium layer, has already been proposed in our copending Japanese Patent Application No. 39092/1982.
Since raw water is filtered from the periphery of the filter medium layer, it is possible to make the best use of the filter medium at the peripheral zone for improving the filtration efficiency.
However, since the channel forming plates are mounted in tiers, raw water inlet points such as raw water distribution ports need be provided for each channel forming plate.